1. Field of the Invention
The present invention relates to a polishing apparatus which polishes and smooths the surface of a substrate such as a wafer, etc., used in semiconductor devices, a semiconductor device manufacturing method using this apparatus, and a semiconductor device manufactured by this manufacturing method.
2. Description of the Related Art
In recent years, as IC's have become finer and more complex, and as the number of layers of multi-layer wiring has increased, the steps on IC surfaces have become increasingly larger, and the precision of polishing wafer surfaces that is performed following the formation of respective thin films has become more important. If the precision of polishing performed following such thin film formation is poor, there is a danger that local thinning of the thin films may occur in step areas, and that faulty wiring insulation or short-circuiting, etc., may occur. Furthermore, in lithographic processes, an out-of-focus state may result if there are numerous indentations and projections in the surface of the wafer, so that it may become impossible to form fine patterns.
Conventionally, a polishing apparatus polishes and smooths the surface of the wafer by causing the surface (undersurface) of the wafer held on the lower part of a spindle to contact a polishing pad bonded to the upper surface of a rotating table while a liquid-form slurry (polishing liquid) containing silica particles is supplied. Japanese Patent Application Kokai No. SHO 11-156711 discloses a polishing apparatus in which the wafer is held on the upper surface side of a rotating table so that the polished state of the wafer surface can be observed during polishing, a polishing member supported on a polishing head that is attached to a spindle is pressed against the wafer surface, and the wafer is polished by causing a polishing pad pasted to the undersurface of the polishing member to contact the wafer surface.
However, in such a polishing apparatus, the polishing surface (polishing pad) has smaller dimensions (a smaller diameter) than the substrate, such as a wafer, etc., that is being polished, and the apparatus is arranged so that the entire surface of the wafer can be polished by causing the polishing head to oscillate with respect to the wafer surface. As a result, in cases where the polishing surface protrudes beyond the outer circumference of the wafer during polishing, the polishing member is tilted, so that the peripheral portions of the wafer are caused to slope downward. Furthermore, the apparatus is arranged so that the contact pressure between the polishing member and the wafer surface is adjusted by means of air pressure that drives the polishing member downward inside the polishing head; however, since such control by means of air pressure has a slow response, the adjustment of the contact pressure cannot be caused to follow the variation in the contact area between the two parts that occurs when the polishing surface protrudes beyond the outer circumference of the wafer. Accordingly, the polished state of the wafer surface tends not to be uniform.